Project Summary/Abstract Wildfires are increasing in frequency, severity, and duration. Climate change and readily-available fuel sources ensure the trend toward increased fire frequency and severity will persist. Moreover, wildfires are not simply a short-term phenomenon; the duration of fire seasons has increased dramatically over the last three decades. Research on the health impacts of wildfires has to date emphasized respiratory health and, to a lesser degree, cardiovascular endpoints. Although a growing body of literature has demonstrated that urban air pollution, specifically PM2.5, is linked to increased risk of miscarriage, lower birth weight, prematurity, being small for gestational age, and developmental conditions such as autism, little research has evaluated influence of wildfires on birth and development in the U.S. Of note, none of this work has been performed in rural areas, which have a unique profile of exposures throughout the year. An urgent need exists to understand impacts to inform strategies for community- and individual-level interventions. We will combine state-of-the-art air pollutant exposure assessment, birth certificate and fetal and infant mortality data, and electronic health records (EHR) to quantify the risk to infants associated with wildfire exposures during pregnancy and identify factors that promote resilience. The association between participant residence-specific estimates of wildfire exposure, overall and by trimester, and birth outcomes in Montana between 2000 and 2017, accounting for exposures occurring throughout the year, will be investigated. Specific outcomes include birth weight, low birth weight status, and small for gestational age status; gestational age at birth and preterm birth status; neonatal intensive care unit admission; fetal death; and infant mortality. EHR will be used to evaluate the impact of wildfire exposures on development in infants born in western Montana in the Providence and Community Medical Center health care organizations between 2012 and 2017. Specifically, we will investigate the effect of wildfire- related PM2.5 exposures on developmental milestone achievement at 2, 4, and 6 months of age. To inform the development of efficacious, practical, and sustainable interventions, we will examine potential effect modification by: individual-level factors, such as maternal education and household income, and community resilience promoting resources, including neighborhood socioeconomic status, social capital, and information and communication capacity. The successful conduct of the proposed research will build capacity for sophisticated spatio-temporal modeling of wildfire-associated air pollutant exposure and expanded and more comprehensive studies of neurodevelopmental impacts of environmental exposures. The proposed project will, for the first time, quantify the impacts of wildfires on birth and development in rural areas and determine resources that confer resilience to these effects. Most importantly, it will inform future interventions designed to mitigate the impacts of this ever-growing threat to public health.